Showing papers on "Slot antenna published in 1999"

Enhanced patch-antenna performance by suppressing surface waves using photonic-bandgap substrates

Abstract: The microstrip patch antenna is a low-profile robust planar structure. A wide range of radiation patterns can be achieved with this type of antenna and, due to the ease of manufacture, is inexpensive compared with other types of antennas. However, patch-antenna designs have some limitations such as restricted bandwidth of operation, low gain, and a potential decrease in radiation efficiency due to surface-wave losses. In this paper, a photonic-bandgap (PBG) substrate for patch antennas is proposed, which minimizes the surface-wave effects. In order to verify the performance of this kind of substrate, a configuration with a thick substrate is analyzed. The PBG patch antenna shows significantly reduced levels of surface modes compared to conventional patch antennas, thus improving the gain and far-field radiation pattern.

A parameter study of stripline-fed Vivaldi notch-antenna arrays

Abstract: A parameter study of Vivaldi notch-antenna arrays demonstrates that the wide-band performance of these antennas can be improved systematically. Stripline-fed Vivaldi antennas are comprised of: (1) a stripline-to-slotline transition; (2) a stripline stub and a slotline cavity; and (3) a tapered slot. The impedances of the slotline cavity and the tapered slot radiator combine at the transition to yield an equivalent series impedance on the feedline. The stripline stub can be represented by a series reactance. The resistance and reactance of the antenna impedance yield insights into the effects of various design parameters. In particular, it is found that the minimum operating frequency can be lowered primarily by increasing the antenna resistance through a change of design parameters. However, beyond a limit for each design parameter, the in-band performance begins to deteriorate. Plots of antenna impedance versus frequency for several parameter variations have been obtained by using a full wave method of moments analysis of infinite arrays. These plots provide a means for designers to systematically improve array performance with bandwidths in excess of 6:1 having been achieved.

Cross-slot-coupled microstrip antenna and dielectric resonator antenna for circular polarization

Abstract: Circular polarization (CP) design of microstrip antennas and dielectric resonator (DR) antennas through a cross slot of unequal slot lengths in the ground plane of a microstrip line is demonstrated. The proposed CP design is achieved by choosing a suitable size of the coupling cross slot, which results in the excitation of two near-degenerate orthogonal modes of near-equal amplitudes and 90/spl deg/ phase difference. This CP design can be applied to both configurations of microstrip antennas and DR antennas and has the advantages of easy fine-tuning and less sensitivity to the manufacturing tolerances, as compared to their respective conventional single-feed CP designs. For the proposed design applied to a low-profile circular disk DR antenna of very high permittivity studied here, a large CP bandwidth, determined from 3-dB axial ratio, as high as 3.91% is also obtained. Details of the proposed antenna designs are described, and experimental results of the CP performance are presented and discussed.

Application of plasma columns to radiofrequency antennas

Abstract: Plasma offers a promising alternative to metal for a wide variety of radiofrequency antenna applications. In this letter we report measurements of efficiencies up to 50% and radiation patterns for plasma column antenna elements. It is demonstrated that the current distribution along the antenna can be controlled by the plasma density. Plasma columns can be used instead of metal elements in communications antennas.

A small planar inverted-F antenna for wearable applications

Abstract: Small printed antennas will replace the commonly used normal-mode helical antennas of mobile handsets and systems in the future. This paper presents a novel small planar inverted-F antenna (PIFA) which is a common PIFA in which a U-shaped slot is etched to form a dual band operation for wearable and ubiquitous computing equipment. Health issues are considered in selecting suitable antenna topology and the placement of the antenna. Various applications are presented while the paper mainly discusses about the GSM applications.

A microstrip patch antenna using novel photonic band-gap structures

Abstract: Printed antennas exemplified by the microstrip patch antenna offer an attractive solution to compact, conformal and low cost design of modem wireless communications equipment, RF sensors and radar systems. Recent applications have pushed the frequency well into the ram-wave region even in the commercial arena as evidenced by the worldwide race to develop advanced collision warning radar systems for automobiles at the 76 GHz band.[1] Microstrip-based planar antennas fabricated on a substrate with a high dielectric constant (Si, GaAs and InP) are strongly preferred for easy integration with the MMIC RF front-end circuitry. However, it is well known that patch antennas on high dielectric constant substrates are highly inefficient radiators due to surface wave losses and have very narrow frequency bandwidth (approximately one to two percent). This situation becomes extremely severe as applications move to higher frequencies, resulting in patch antennas with reduced gain and efficiency as well as an unacceptably high level of cross polarization and mutual coupling within an array environment. Therefore, much effort has been made recently to realize high efficiency patch antennas on high permittivity substrates, including using the latest micromachining technology.[2,3]

Plane collapsible double-input antenna

Abstract: FIELD: transceiving equipment of radio-communication systems including space communication and television systems SUBSTANCE: antenna has two antenna panels with alternating rectangular and U-shaped radiating waveguides for transmitting and receiving channels, respectively, provided with transverse and longitudinal slots, respectively Dumbbell-shaped transverse slots are fed in traveling- wave mode by pairs of asymmetric capacitive diaphragms placed on opposite wide walls of rectangular radiating waveguide Changing magnetic field position every half-wave is effected by reversing shift sign of capacitive-diaphragm pairs which provides for in-phase excitation of all dumbbell-shaped radiating slots Changing diaphragm size ensures single-ended matching of each slot and distribution of slot excitation intensity decaying to ends, as well as desired level of directivity pattern side lobes of antenna Rectangular radiating waveguides are fed in their center through longitudinal dumbbell- shaped slots coupled with rectangular waveguide feeds of same width which are combined by E-adders placed on second tier of antenna panel Longitudinal radiating slots are alternately shifted towards two side walls of U-shaped radiating waveguide Single-ended matching of each longitudinal slot is provided by asymmetric capacitive and inductive diaphragms as well as by slot on partition edge U-shaped radiating waveguide is fed from rectangular waveguide feed through transverse dumbbell slot and partition slot Waveguide feeds and transverse feeding slots are combined by E-adders placed on second tier of antenna panel E-adders of transmitting and receiving channels are combined by series T-junctions When collapsed, antenna panels are arranged one on top of other In working position, they are placed on same plane immediately adjacent to each other EFFECT: improved level of directivity pattern side lobes 17 dwg

Single-feed slotted equilateral-triangular microstrip antenna for circular polarization

Abstract: Novel designs of single-feed equilateral-triangular microstrip antennas for circular polarization (CP) are proposed and studied experimentally. It is demonstrated that by embedding a narrow slot or a cross slot of unequal slot lengths in the triangular patch, circularly polarized radiation of microstrip antennas can easily be achieved using a single probe feed. Furthermore, results show that for the design with a cross slot, the proposed antenna can perform CP radiation with a reduced antenna size at a given frequency (denoted as compact CP operation here); that is, the required antenna size is smaller for the proposed antenna for performing CP radiation as compared to a conventional circularly polarized triangular microstrip antenna at a fixed operating frequency. Details of the proposed CP designs are described, and typical experimental results are presented and discussed.

Integrated-antenna push-pull power amplifiers

Abstract: In this paper, the integrated-antenna concept is applied to push-pull power amplifiers (PAs). In this approach, the antenna serves as an out-of-phase power combiner and tuned load for higher harmonics. This new architecture effectively has a near-zero loss output hybrid, and results in a high-efficiency PA. The first example is a narrow-band push-pull amplifier integrated with a dual-feed patch antenna. At an operating frequency of 2.5 GHz, a maximum measured power-added efficiency (PAE) of 55% is achieved. The second example is a broadband push-pull amplifier integrated with a dual-feed slot antenna amplifier operating at 2.46 GHz which has a peak PAE of 63%, and PAE better than 55% in an 8% bandwidth. Additionally, 48% PAE is achieved with code-division multiple-access modulation and adjacent-channel power ratio better than -42 dBe at a 1.25-MHz offset.

Study of a CPW inductively coupled slot antenna

Abstract: Coplanar waveguide (CPW) fed slot antennas are attractive due to fabrication simplicity and ease of integration with active devices. A new concept for exciting slots with a CPW line based on inductive coupling is presented. It is described how this coupling structure can be designed to tune the impedance of the antenna over a wide range. Single elements and arrays designed for 5- and 25-GHz operation are described. Simulated and measured characteristics are presented. This new coupling topology is particularly suitable for series-fed array configurations and broad-band design.

Extended dielectric material tapered slot antenna

Abstract: A tapered slot antenna (20) includes a dielectric (22) with a metallization layer (24) deposited on one side. The metallization layer (24) is etched to the dielectric substrate (22) to form a tapered slot (26, 28, 30, 32). In order to tune the antenna 20), for example, such that the E and H field beam width are symmetrical, the (22) extends beyond the wide portion of the slot as a dielectric loading (26, 28, 30, 32). A microstrip feed line (40, 42, 44, 46) is formed by a metallization deposit on an opposing side of the substrate (22). The microstrip feed line (40, 42, 44, 46) extends across a narrow portion of the tapered slot (26, 28, 30, 32) and is configured to optimize the coupling between the microstrip feed line (40, 42, 44, 46) and the tapered slot antenna (20).

Bow-tie slot antenna fed by CPW

Abstract: A bow-tie slot antenna fed by CPW is introduced. It is designed to work in the Ku- band around 15.5 GHz. The proposed antenna is analysed both theoretically and experimentally. The presented results include the return loss and the radiation patterns. Two different geometries of the bow-tie antenna are presented and compared. The proposed antenna has several advantages such as a very large bandwidth, good control of its input impedance, and ease of fabrication. The proposed antenna has a dipole like radiation pattern which makes it suitable for mobile communication systems designed to work in the Ku- band.

A method for designing broad-band microstrip antennas in multilayered planar structures

Abstract: The narrow bandwidth of a microstrip antenna is one of the important features that restrict its wide usage. A simple and practical method for the design of broad-band microstrip antennas is presented in this paper. Utilizing this design technique, several two-layer microstrip antennas have been proposed. To confirm the applicability of the method for the designs of antennas at L-band, experiments have been carried out. The measured results show that the proposed antennas have a bandwidth of up to 25.7%. Also, the method proposed in this paper is applicable to the design of other types of multilayered planar antennas.

A 77-GHz FM/CW radar front-end with a low-profile low-loss printed antenna

Abstract: Design and results of a 77-GHz frequency-modulation/continuous-wave radar sensor based on a simple waveguide circuitry and a novel type of printed, low-profile, and low-loss antenna are presented. A Gunn voltage-controlled oscillator and a finline mixer act as transmitter and receiver, respectively, connected by two E-plane couplers. The folded reflector-type antenna consists of a printed slot array and another planar substrate, which, at the same time, provides twisting of the polarization and focusing of the incident wave. The performance of the radar is described, together with the initial results of a scanning of the antenna beam.

Diversity transmission in a Mobile Radio System

Abstract: In a known diversity transmission method, two signals with different identifications are transmitted via two spaced antennas. To be able to apply the diversity principle to more than two antennas, a novel method and a novel base station are proposed. The novel base station comprises two transmitting apparatuses and an assignment apparatus connected thereto which establish connections between each of the two transmitting apparatuses and each of the antennas. The base station further comprises a computing and control apparatus that is connected to the assignment apparatus, which divides the antennas into a first antenna group and a second antenna group, and controls the switching of the connections in such a way that the first antenna group is connected to the first transmitting apparatus, and the second antenna group to the second transmitting apparatus. By several different divisions of the antennas into a first antenna group and a second antenna group, the amplitude and phase differences (phi) existing between the signals at the receiver can be compensated for even if more than two antennas are used. It is also possible to determine that grouping of the antennas with which the highest diversity gain is achieved.

Linearly polarized radial-line slot-array antennas with improved return-loss performance

Abstract: The standard linearly polarized radial-line slot-array (RLSA) antenna exhibits poor return loss as seen by its coaxial feed. This paper describes techniques that improve the poor return-loss performance of this antenna, by using two interchangeable methods: i) reflection-canceling slots on the front and back surface of the antenna, and ii) beam squinting. A series of 550 mm diameter linearly polarized Ku-band prototype antennas were constructed to experimentally investigate the efficiency of each of these methods. In order to cut experimental costs, initial radiation-pattern modeling was performed theoretically, and then prototypes were developed using inexpensive aluminum foil. Measurements of the developed prototypes indicated that both the reflection-canceling and beam-squinting methods provided a substantial improvement in return loss over the desired frequency band.

Rigorous analysis of probe-fed printed annular ring antennas

Abstract: This paper presents calculated and measured results for the input impedance and radiation performance of probe-fed printed annular ring antennas. Geometries featuring stacked rings as well as shorting posts are considered. A numerical model is presented that is based on a full-wave spectral-domain moment-method solution. In this solution, a specialized attachment mode-expansion function is used to model the connection between the probe feed and the printed ring. Measured results are presented and compare well with the theory. Annular rings are found to have certain advantages over circular and rectangular microstrip antennas.

Beamformer architectures for active phased-array radar antennas

Abstract: In active phased-array antennas, the transmit and receive functions are distributed at the antenna aperture using transmit and receive (T/R) modules. The use of T/R modules provides a significant improvement in antenna performance and flexibility in the choice of array architectures. We present a review of various beamformer architectures for active phased-array antennas. This review is limited to corporate-fed active phased-array antennas for radar applications. Beamformer architectures for narrow and wide bandwidth arrays, including the choice of applying an amplitude taper in the T/R module or beamformer network are discussed. Beamformer architectures that increase antenna reliability are also presented.

Millimeter-wave tapered-slot antennas on synthesized low permittivity substrates

Abstract: This paper presents 30-GHz linear-tapered slot antennas (LTSA) and 94-GHz constant-width slot antennas (CSWA) on synthesized low dielectric constant substrates (/spl epsiv//sub r/=2.2). The performance of tapered-slot antennas (TSA) is sensitive to the effective thickness of the substrate. We have reduced the effective thickness by selectively machining holes in the dielectric substrate. The machined substrate antenna radiation patterns were significantly improved independent of the machined hole size or lattice as long as the quasi-static effective thickness remained the same, even if the hole/lattice geometry is comparable to a wavelength. The method was applied at 94 GHz on a CSWA with excellent radiation pattern improvement, making it suitable for f/1.6 imaging array applications.

A two-beam slotted leaky waveguide array for mobile reception of dual-polarization DBS

Abstract: A two-beam slotted leaky waveguide array for mobile reception of dual-polarization direct broadcast from satellite (DBS) is realized in a single-layer structure. Two feed waveguides attached at both ends of cross-slotted radiating waveguides excite the leaky waves propagating in opposite directions. Each of them radiates either of two circularly polarized waves in symmetrical beam directions. Balanced design of two beams for each polarization imposes symmetry in the array design of slots. The slot coupling distribution is optimized for the maximum gain under this symmetry condition. A model antenna in about a 300-mm square is fabricated for experiments in the 12-GHz band. Antenna efficiency of 71% and 64% is obtained for each beam in different polarizations.

Circularly polarised circular ring slot antenna fed by stripline hybrid coupler

Abstract: A novel circular ring slot antenna which has a stripline hybrid coupler feed network is proposed for generating broadband circular polarisation performance. A broad impedance bandwidth (VSWR 2:1) at 20.5% and a CP bandwidth at 9% for a <3 dB axial ratio have been achieved.

Feed structures for tapered slot antennas

Abstract: A suspended microstrip line structure for feeding a tapered slot antenna has a ground layer separated by means of an air gap from a dielectric slab with a strip line conductor feed running on the surface of the dielectric. The strip line may run along the surface of the dielectric which faces away from the ground layer, or the structure may be inverted such that the strip line runs along the surface of the dielectric which faces the ground layer. These suspended microstrip line structures exhibit lower transmission loss. In another embodiment, a printed transmission line having a slot in its ground layer feeds a tapered slot antenna element which lies in a plane which intersects, and so is not parallel to, the printed transmission line structure. The ground layer slots cut the current on the ground of the transmission line and couple energy from the line to the tapered slot antenna element. Altering the configuration of the ground layer slots allows the antenna to efficiently operate within different frequency bands without changing the dimensions or parameters of the tapered slot antenna or the printed transmission line. The printed transmission line is preferably a suspended microstrip line. One and two dimensional arrays of these antenna elements fed by a parallel beam forming network (BFN) may also be assembled.

Multiple resonances and polarisation of U-slot patch antenna

Abstract: Multiple resonances and polarisation of a single layer probe fed wideband microstrip U-slot patch antenna are discussed. Results show that the radiation characteristics, such as polarisation and gain, are modified within the bandwidth owing to the excitation of resonant modes orthogonal to each other.

Personal communication terminal with a slot antenna

Abstract: A personal communications terminal includes a telephone unit and an application processing unit that are operatively connected. The telephone unit includes a first RF transceiver for communicating with a cellular communications network via an external dipole antenna. The application processing unit includes a short range transceiver and antenna for connecting the computing device with an external computer or local area network. The short range antenna is a slot antenna formed by a slot in the housing of the personal communications terminal.

Antennas on high-impedance ground planes

Abstract: A new type of metallic electromagnetic structure has been developed that is characterized by having high surface impedance. Unlike normal conductors, this new surface does not support propagating surface currents, and it reflects electromagnetic waves with no phase reversal. This unique material can serve as the ground plane for new kinds of low-profile antennas.

On-wafer characterization of millimeter-wave antennas for wireless applications

Abstract: This paper demonstrates a deembedding technique and a direct on-substrate measurement technique for fast and inexpensive characterization of miniature antennas for wireless applications at millimeter-wave frequencies. The technique is demonstrated by measurements on a tapered slot antenna (TSA). The measured results at Ka-band frequencies include input impedance, mutual coupling between two TSA's, and absolute gain of TSA.

Design of Radial Line Slot Antennas at 8.3 GHz for Large Area Uniform Plasma Generation

Abstract: A radial line slot antenna (RLSA) 400 mm in diameter is designed for a plasma source at 8.3 GHz as a candidate for a large area high density plasma source with a narrow process space. A RLSA with paired slots arrayed concentrically on its aperture is designed and applied to a plasma process system which does not need a magnetic field. First, electrical performance without plasma is predicted and measured. Reasonable voltage standing wave ratio (VSWR) as well as uniform field distribution on the antenna aperture is realized. As applied to the plasma test equipment, high electron density of more than 1?1012 cm-3 as well as fairly uniform (?2%) distribution at a low electron temperature is produced in the vicinity of the antenna aperture through a quartz glass window. Control of uniformity in ion flux profiles by blocking the antenna aperture is demonstrated.

Multiband antenna system using rf micro-electro-mechanical switches, method for transmitting multiband signals, and signal produced therefrom

Abstract: A method and system for transmitting, and a signal comprising multiple frequency bands from a single slot antenna are disclosed. The system comprises a slot antenna and a micro-electro-mechanical (MEM) switch, coupled to the slot antenna. The MEM switch is opened and closed, thereby changing the resonant frequency of the slot antenna. The slot antenna transmits a first frequency when the MEM switch is open and a second frequency when the MEM switch is closed. The method for transmitting a first frequency and a second frequency from a slot antenna comprises the steps of transmitting the first frequency from the slot antenna, closing a micro-electro-mechanical (MEM) switch coupled across the slot antenna, therein changing the resonant frequency of the slot antenna, and transmitting the second frequency from the slot antenna after the MEM switch is closed. A signal comprising a first and second frequency in accordance with the present invention is transmitted by an array of antennas, wherein the array of antennas comprises at least one slot, the slot being reconfigurable through a RF MEM switch coupled to the slot, by performing the steps of transmitting the first frequency from the slot antenna, closing a micro-electro-mechanical (MEM) switch coupled across the slot antenna, therein changing the resonant frequency of the slot antenna, and transmitting the second frequency from the slot antenna after the MEM switch is closed.

Broadband fixed-radius slot antenna arrangement

Abstract: A fixed radius tapered slot antenna ( 100 ) formed a dielectric substrate ( 10 ) with an electrically conductive layer ( 14 ) on one side. The slot is defined by two hemispherical shaped elements ( 12, 13 ). A common base ( 15 ) is also formed on the conductive layer behind the hemispherical shaped members. Preferably, a microstrip feedline ( 16 ) is formed on the side of the dielectric substrate to electromagnetically couple to the balun (18) adjacent the narrow end of the tapered slot. A contiguous array of fixed radius tapered slot antennas ( 100 ) can he made on the same conductive layer of a dielectric layer. A reflector can he integrated with the antenna array to improve the radiation pattern. The fixed radius tapered slot antenna has been proven to out-perform an exponentially tapered slot or Vivaldi antenna.

Analysis and design of coplanar waveguide-fed slot antenna array

Abstract: A method for analyzing and designing the slot antenna array excited by a coplanar waveguide (CPW) is presented. The slots are etched on the conducting plane of the CPW and placed in the direction perpendicular to the transmission line. Moment-method analysis and matrix-pencil approach are adopted to calculate the scattering parameters and hence the self-admittance of each slot. The mutual admittances between the slots are calculated from the formulas derived for the complementary strip dipoles based on the reciprocity theorem and via Booker's relation. Then the transmission line theory is used to calculate the input impedance of the array, and an iterative process is employed to obtain a matched design for a desired slot-voltage distribution. A four-element slot array is fabricated and measured using this design procedure. Calculated results are in good agreement with measurements.